package com.yang.sqlSession;

import com.sun.org.apache.bcel.internal.generic.NEW;
import com.yang.config.BoundSql;
import com.yang.pojo.Configuration;
import com.yang.pojo.MappedStatement;
import com.yang.utils.GenericTokenParser;
import com.yang.utils.ParameterMapping;
import com.yang.utils.ParameterMappingTokenHandler;
import com.yang.utils.TokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {
    @Override                                                                                         //user
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //1.注册驱动,获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //2.获取sql语句, select * from user where id = #{id} and username = #{username}
        //  转换为sql语句, select * from user where id =? and username =? , 转换的过程中还需要对#{}立面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql =  getBoundSql(sql);
        //3.获取预处理对象:prepareStatement 预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //4.设置参数
            //获取参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            //设置暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }
        //5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();
        //6.封装返回结果集
        while (resultSet.next()){
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount() ; i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省.根据数据库表和实体的对应关系,完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objects.add(o);
        }
        return (List<E>) objects;

    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if (paramterType!=null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }else {
            return null;
        }

    }

    /**
     * 对#{}的解析工作:1.将#{}使用 ? 进行代替;2.解析出#{}里面的值进行解析存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类:配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parse = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parse,parameterMappings);

        return boundSql;
    }
}
